In the composite industry, several types of designs and shapes are used as cores, sandwiched between layers of reinforcing materials (also referred to as the outer skin) and surrounded by various resins to produce a strong, lightweight composite structure. Honeycomb core sandwich panels have been used as high performance structural elements in advanced composite industries such as aerospace, marine and automotive. Honeycomb cores and sandwich panels for industrial and military applications have been typically made of thermoplastic, aluminum, Nomex and machined honeycomb. Metal/plastic honeycomb panels with custom bonding and custom finishes are available to the present industry. The prior art honeycomb type structures have cells that are contiguous, connected and/or interlocked. The cells are not separated and do not have a space between them. This type of design does not allow for the flow of resin or other bonding material between the cells nor does it allow for a resin bond between the upper and lower skins or layers of reinforcing materials.
The most common materials used for cores are wood (plywood), end grain balsa, plastic and several types of foams designed to accept differential stresses and loads. These materials are handicapped by: (1) delamination from localized impacts; (2) delamination and rot from water and moisture intrusion around fasteners and through cracks in damaged skins; (3) expensive and time consuming manufacturing processes; (4) low strength due to delamination of the outer skin layers of reinforcing materials; (5) manufacturing processes that require vertical channels to allow for resin flow from one layer of the laminate to the other; and (6) environmentally dangerous vapor emissions caused by the application of the resins to the outer skin of reinforcing materials.
Some of the above problems with the present state of the art is a result of the manufacturing and assembly process. Typically, the reinforcing material is placed on each side of the core and resin is then spread over one or both sides of the reinforcing material. There is no direct resin bond between the top and bottom layers or skins of reinforcing material or between core cell members leading to delamination problems and reduced strength. The resin is usually applied by hand in an open environment leading to the escape of environmentally hazardous vapors.
The present core invention is designed to simplify the manufacturing process, to provide for reduced delamination failures and to provide for a stronger, lighter and more versatile composite structure. The manufacturing process can be performed in a closed production mold allowing for simpler and less expensive manufacturing. The closed molding process also prevents the escape of hazardous vapors into the environment.